1. Field of the Invention
The invention relates to a light source module and a projection apparatus, and more particularly, to a light source module with high brightness and a projection apparatus having the light source module.
2. Description of Related Art
Along with the progress of display technology, a projection apparatus can adopt different light sources, in which in addition to adopting an ultra high pressure lamp (UHP lamp) emitting white light in association with a color wheel to sequentially produce red light, green light and blue light, such that the projection apparatus is able to provide colorful image frames. Recently, red light emitting diode (LED), green LED and blue LED are also used to serve as a light source for a projection apparatus.
In a projection apparatus with LEDs as a light source, the light beams emitted from red, green and blue LEDs would be combined through a combining-light system, so that the different color light beams along different transmission directions are guided to a same direction. The luminance of a projector bases on the construction depending on the brightness of the LEDs. Especially, the green LED plays a role as a major light source of the LEDs for contributing the brightness of the construction, so that the total luminance of the projector is limited by the light-emitting efficiency of the green LED. However, the light-emitting efficiency of the green LED currently is not high and unlikely good as the light source of a projector with high luminance (for example, greater than 2000 ANSI lumens). In this regard, some projectors use a hybrid light source so as to increase the luminance of the projector.
For example, the hybrid light source is designed by using a blue laser light to excite the green phosphor powder on a color wheel, so that the blue laser light is converted into a green light. At the time, the combining-light system is used to combine the green light with the blue and red lights respectively emitted from a blue LED and a red LED so as to provide the projector with a required illumination light source. In addition, in the current technology, usually a lens is disposed before the color wheel to collect the green light after the above-mentioned conversion so as to increase the light-converging efficiency for the green light. However, to avoid the color wheel and the lens from being interfered with each other, a specific distance between the color wheel and the lens must remain, which limits the light-converging efficiency of the lens. On the other hand, to meet the design requirement of the hybrid light source, the combining-light system requires an additional dichroic mirror to change the optical transmission path of the longer wavelength light, followed by combining the longer wavelength light with other color light. As a result, more optical components are employed here and the light loss would be relatively more after passing through the optical components.
Several patents relating to illumination models are provided. For example, U.S. Pat. Nos. 7,618,158 and 7,232,228 disclose an illumination system, wherein a light source is disposed at a first focal point of a reflector so that the light beam emitted from the light source is converged at a second focal point. Additionally, U.S. Patent Application No. 20080030993 discloses a scheme that an LED or a laser diode (LD) is disposed in a reflective cup to excite a wavelength conversion material so that a shorter wavelength light and a longer wavelength light are mixed by each other to produce a white light.